Astronomy Homework 12

HOMEWORK 12- CHAPTER 8

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Question 17: B

Question 23: There are various ways in which the two types (terrestrial and gas) of planets in our solar system contrast:

1. They differ in size. The largest terrestrial planet is Earth with a diameter of 8000 miles. The smallest gas planet is Neptune and its diameter is 30800 miles.

2. The length of one year is different. Mars has the longest one-year period between the terrestrial planets and that is of 686 Earth days, however it is of no comparison to the length of a year on the gas planets. The shortest year of a gas planet is equivalent to 12 Earth years.

3. Gas giants have shorter days than terrestrial planets. A day on Jupiter and Saturn is about 10 hours long.

4. Gas planets are on the outside of the asteroid belt farther from the sun thus cooler than the terrestrial planets which are on the inside of the asteroid belt making them much warmer.

Question 41: The very high pressure in their cores (about 2 mil bars) and high temperature (10,000 K) made the formation of metallic hydrogen possible where the electrons are stripped free and hydrogen acts like a liquid metal. We call it metallic because it can conduct electricity.

Question 55:

Brightness decreases with the square of the distance.

We are 1 AU from the Sun.

If we were 2 Au away, it would appear 4 times fainter.

To be 400,000 times fainter then we need to be sqrt(400,000)=632.46 AU away from our current position.

Neptune orbits the Sun at an average distance of 30.1 AU → 632.46/ 30.1 = 21.01 times.

Thus, 21 time the distance of Neptune.

Question 62:

Because Saturn is smaller and further away from the Sun, it should be dimmer than Jupiter but in fact it shines with energy 2.3 times of what it receives from the Sun.